Body fluid sampling apparatus

ABSTRACT

A body fluid sampling apparatus (A), comprising a piston ( 11 ) provided in a tubular main case ( 10 ), a first plunger rod ( 12 ) extending into the piston ( 11 ) integrally with each other; a first spring ( 13 ) elastically energzing the piston ( 11 ) toward the upper end side, a second plunger rod ( 15 ) installed in the first plunger rod ( 12 ) through a second spring ( 14 ), a lancet mounted body ( 16 ) provided on the second plunger rod ( 15 ) and having a lancet (B) mounted therein, a third spring ( 17 ) elastically energizing the lancet mounted body ( 16 ) toward the upper end side, latch mechanisms ( 20, 30 ) suppressing the second plunger rod ( 15 ) and first plunger rod ( 12 ) when the first plunger rod ( 12 ) is moved to the lower end side by he push-down of the piston ( 11 ), and a release mechanism ( 40 ) for releasing the locked state of the first plunger rod ( 12 ) and the second plunger rod ( 15 ).

TECHNICAL FIELD

The present invention relates to a body fluid sampler for sampling bloodfor example for measuring the glucose concentration in the blood(hereinafter referred to as “blood sugar level”) for example.

BACKGROUND ART

For the treatment of diabetes, it is necessary to maintain the bloodsugar level to a normal range. Particularly for the treatment ofinsulin-dependent diabetes mellitus, a patient needs to conduct insulininjection by himself or herself to keep the blood sugar level to anormal range. In this case, the patient needs to appropriately check theblood sugar level to determine whether the blood sugar level is withinthe normal range.

Generally, for sampling blood to measure the blood sugar level, use maybe made of a portable blood sampler which internally holds, at the tipend of the apparatus, a piercing needle called lancet. In using such ablood sampler, the skin of the patient is instantaneously stabbed by thepointed tip of the lancet. The patient causes the blood sampler to drawblood from the stabbed portion and applies the sampled blood to a bloodtest piece. In this way, the determination of the blood sugar level canbe performed relatively easily.

Such a prior art blood sampler is disclosed in JP-A-5-95937 orJP-A-10-127610 for example. In the prior art sampler disclosed in theformer publication, while the tip end of an apparatus body is pressedagainst the skin of a forearm, a push member is pushed down by a thumbagainst the repulsive force of a coil spring, thereby stabbing thepointed tip of a lancet into the skin under magnetic action. Thereafter,by retreating the pressing member together with the lancet, the pointedtip of the lancet is removed from the skin. At this time, the air in theinterior of the apparatus body undergoes a pressure reduction to causethe stabbed portion to bulge for prompting blood bleeding from theportion stabbed by the lancet.

The prior art sampler disclosed in the latter publication solelyutilizes the repulsive force of a spring for pushing down a push memberprovided at the upper end of an apparatus body to stab the skin with alancet followed by skin bulging. In use, specifically, the push memberprovided at the upper end is first pulled up to make the apparatus readyfor use. Then, with the tip end of the apparatus pressed against theskin of a forearm for example, the push member is pushed down by athumb. As a result, the air within the apparatus body escapes to theoutside through a non-return valve. When the push member is furtherdepressed, the pointed tip of the lancet stabs the skin. By subsequentlyremoving the thumb from the push member, the force of the spring causesthe push member to move back upward. At this time, the interior of theapparatus body undergoes a pressure drop, causing the stabbed portion tobulge. Finally, the push member is pushed down again to relieve thevacuum state within the apparatus body back to the atmospheric pressure,consequently allowing the tip end of the apparatus body to be removedfrom the skin.

However, the above-described blood samplers have the followingdrawbacks.

In the prior art sampler disclosed in the former publication, the pushmember is depressed by one thumb with the tip end of the apparatus bodypressed against the skin. In this prior art sampler, however, the airtrapped in the apparatus body is compressed, so that a considerablepower is required to push down the push member. Moreover, the pushmember need be pushed down by a considerable stroke. Therefore, thehandling of the apparatus by one hand is extremely difficult for apatient having an insufficient force. Further, in depressing the pushmember with the tip end of the apparatus body pressed against the skin,the patient may fear that the pointed tip of the lancet stabs deeply inthe skin particularly when the stroke of the push member is long.Moreover, since the prior art sampler is not provided with means forrelieving the vacuum in the apparatus body, blood may splash in removingthe pointed tip of the apparatus body from the skin.

Since the prior art sampler disclosed in the latter publication alsosamples blood only by the operation of the push member, it has the samedrawbacks as those of the foregoing prior art sampler. Particularly inthis prior art apparatus, the push member need be depressed again torelieve the vacuum state within the apparatus. Therefore, there is apossibility that the lancet stabs the skin again when the push member isexcessively depressed.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a bodyfluid sampler which is capable of eliminating or at least lessening theabove-described problems.

According to the present invention, there is provided a body fluidsampler comprising a cylindrical main case having a first end providedwith a first opening and a second end provided with a second opening, apiston inserted in the main case to project from the first opening formovement within the main case airtightly with respect to an inner wallof the main case, a first plunger rod extending integrally from thepiston toward said second end, a first elastic member for elasticallyurging the piston toward said first end, a second plunger rod extendingfrom the first plunger rod toward said second end for movement withinthe main case with a compressible second elastic member interposedbetween the first plunger rod and the second plunger rod, a lancet mountassociated with the second plunger rod adjacent to said second end formovement within the main case, the lancet mount being provided with alancet oriented toward said second end, third elastic member forelastically urging the lancet mount toward said first end, latchmechanism which works, when the piston is pushed down for movementtoward said second end together with the first plunger rod, forrestricting movement of the second plunger rod toward said second endagainst a pushing force of the second elastic member and for restrictingrebounding of the piston and first plunger rod which have been movedtoward said second end while allowing the second elastic member to becompressed, and a release mechanism for releasing the first plunger rodand second plunger rod which have been latched by the latch mechanism.

Specifically, the latch mechanism includes a first and a secondengagement members each of which has a stopper for stopping acorresponding one of the first and the second plunger rods, a latchingelastic member for elastically biasing each of the engagement memberstoward the corresponding one of the first and the second plunger rods,and engagement portions respectively formed on the first and the secondplunger rods, the engagement portions being spaced from each other by adistance which is larger than a distance between the stoppers when theplunger rods are held in an initial state, the release mechanismincluding a release button for simultaneously releasing the stoppersfrom the corresponding engagement portions against an elastic biasingforce of the latching elastic member.

In the above-described body fluid sampler, the piston moves toward thesecond end of the main case when it is depressed by the user. As aresult, the second elastic member is elastically compressed between thefirst and the second plunger rods, thereby storing an elastic restoringforce. The engagement portion of the first plunger rod engages thestopper of the first engagement member with the first plunger rod biasedtoward the first end by the second elastic member. The engagementportion of the second plunger rod engages the stopper of the secondengagement member with the second plunger rod biased toward the secondend by the second elastic member. In this way, the both plunger rods arerestricted.

Subsequently, the user pushes the release button of the releasemechanism with the second opening of the main case pressed against theskin. When the release button is pushed, the second plunger rod hits orpushes the lancet mount downward due to the elastic force of the secondelastic member. Thus, the pointed tip of the lancet instantaneouslystabs the skin facing the second opening of the main case. The firstplunger rod and the piston return to respective positions before theoperation due to the elastic restoring force of the second elasticmember and the first elastic member. As a result, the interior of themain case undergoes a pressure reduction to cause the stabbed portion tobulge for prompting blood bleeding from the stabbed portion.

In this way, according to the above-described body fluid samplingapparatus, the preparation for launching the lancet B can be completedby depressing the piston before bringing the second end of the main caseinto pressing contact with the skin. Since the interior of the main caseis held at the atmospheric pressure at this time, even a patient havingan insufficient force can conduct the operation by one hand. Moreover,the stroke for depressing the piston is not so long, the user can handlethe body fluid sampler easily without anxiety.

According to a preferred embodiment of the present invention, therelease button is provided with a push portion projecting from apredetermined portion of a side surface of the main case while keepingairtightness relative to the main case.

With this structure, even when the release button is operated, theairtightness of the main case is maintained. Therefore, just by oncepushing the release button, the stabbing of the skin by the lancet andthe pressure reduction in the main case can be carried outinstantaneously and easily without causing pain to the patient.

According to a preferred embodiment of the present invention, the maincase may be provided with a vacuum relief mechanism for relieving avacuum state within the main case generated by pulling back the pistontoward said first end.

Preferably, the vacuum relief mechanism may be provided with a vacuumrelief button partially projecting from a predetermined portion of aside surface of the main case, the vacuum relief button beingelastically urged in the projecting direction while keeping airtightnessof the main case, the vacuum relief button being pushed against theelastic urging force for allowing air passage between inside and outsideof the main case.

With this structure, after the stabbing of the skin by the lancet andthe pressure reduction in the main case are completed, the pressure inthe main case can be returned to the initial atmospheric pressure justby once operating the vacuum relief button. Thus, the second end of themain case formed with the second opening can be easily removed from theskin.

According to a preferred embodiment of the present invention, the pistonhas an outer circumferential wall provided with an O-ring for closelycontacting the inner wall of the main case.

With this structure, the airtightness between the piston and the maincase is sufficiently maintained by the O-ring. Therefore, the pressurewithin the main case can be sufficiently reduced by pulling up thepiston to the initial position.

Other features and advantages of the present invention will becomeclearer from the detailed description given below with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a body fluid sampler embodying thepresent invention.

FIG. 2 is a sectional view taken on lines II—II of FIG. 1.

FIG. 3 is an enlarged sectional view showing a portion III of FIG. 2.

FIG. 4 is a sectional view showing the first operation of the body fluidsampler.

FIG. 5 is a sectional view showing the first operation of the body fluidsampler.

FIG. 6 is a sectional view showing the second operation of the bodyfluid sampler.

FIG. 7 is a sectional view showing the third operation of the body fluidsampler.

FIG. 8 is an enlarged sectional view of the principal portion shown inFIG. 7.

MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowwith reference to the accompanying drawings. Throughout the drawings,the elements which are identical or similar to each other are designatedby the same reference signs. In the drawings, hollow arrows indicate thedirection of the operation by the user, whereas thin arrows indicate thedirection of movement of a part or the direction of air flow.

First, reference will be made to FIGS. 1 through 3. These figuresillustrate a body fluid sampler A, according to the present invention.The body fluid sampler A, which is a portable medical instrument usedfor the self-sampling of blood for example, holds a lancet B forallowing its instantaneous upward and downward movement. The body fluidsampler A comprises a main case 10, a piston 11, a first and a secondplunger rods 12, 15, a first through a third springs 13, 14, 17, alancet mount 16, a cap 18, a first and a second latch mechanisms 20, 26,a release mechanism 30 and a vacuum relief mechanism 40 and soon. Thelancet B comprises a columnar solid body B2 integrally formed with apointed tip B1 in the form of a needle tip.

The main case 10, which comprises a hollow cylinder of a portable size,has an upper end to which a head cover 10 a is attached. The head cover10 a is formed with an upper end opening 10A for inserting the piston11. The main case 10 has a lower end to which a lower cover 10 b isattached. The lower cover 10 b is formed with a lower end opening 10Bfor allowing vertical movement of the lancet B. The main case 10 definesa case chamber 10 c which communicates, through the lower end opening10B of the lower cover 10 b, with the internal space of the cap 18attached to the lower end of the lower cover 10 b.

The piston 11 has an upper end 11 a projecting from the head cover 10 athrough the upper end opening 10A. The piston 11 has a bottom portion 11b inserted in the case chamber 10 c. In operation, the upper end 11 a ofthe piston 11 is depressed by the user's finger or thumb for example.The bottom portion 11 b of the piston 11 has an outer diameter whichcoincides with the inner diameter of the case chamber 10 c. The bottomportion 11 b of the piston 11 is formed, at the outer circumferentialsurface thereof, with an O-ring 11 d which closely contacts the innerwall of the case chamber 10 c for airtight sealing. With thisarrangement, the piston 11 is airtightly movable up and down in the casechamber 10 c.

The first plunger rod 12 is integral with the piston 11 and projectsdownward from the bottom portion 11 b of the piston 11. The firstplunger rod 12 is formed, at a longitudinally intermediate positionthereof, with an engagement portion 12 a which is tapered to provide aradially extending flat bottom surface. The first plunger rod 12 has alower end integrally formed with a spring holder 12 b. The spring holder12 b comprises a generally hollow cylinder for holding the spring 14therein.

The first spring 13 has an upper end 13 a fixed to the main case 10 anda lower end 13 b fixed to the piston 11. As the piston 11 movesdownward, the first spring 13 works to pull back the piston 11 upward byits elastic restoring force. Specifically, when the first spring 13,which is normally held in a state shown in FIG. 2, is tensioned, itelastically pulls back the piston 11 upwardly.

The second spring 14 has an upper end fixed to the spring holder 12 band a lower end fixed to the upper end of the second plunger rod 15. Thesecond spring 14 works to elastically push back the first and the secondplunger rods 12, 15 upward and downward, respectively. Specifically,when the second spring 14 is compressed from its normal state shown inFIG. 2 by the first and the second plunger rods 12, 15, it works toelastically push back these rods.

The second plunger rod 15 is connected, via the second spring 14, to alower portion of the first plunger rod 12. The second plunger rod 15 isformed, at a longitudinally intermediate position thereof, with anengagement portion 15 a which is tapered to provide a radially extendingflat upper surface.

The lancet B is mounted to and held by the lancet mount 16. The lancetmount 16 is held by a third spring 17 in facing relationship to thelower end 15 b of the second plunger rod 15 with a predetermined spacingtherefrom. The lancet mount 16 is movable up and down in accordance withthe elastic deformation of the third spring 17. It is to be noted thatthe lancet B is removable from the lancet mount 16 with the pointed tipB1 oriented downward.

The third spring 17 has an upper end 17 a fixed to the lancet mount 16and a lower end 17 b fixed to the inner side of the lower cover 10 b.When the lancet mount 16 is moved downward, the third spring 17 works toelastically force the lancet mount 16 upward for recovery to its normalposition. Specifically, when the third spring 17 is compressed from itsnormal state shown in FIG. 2, it elastically pushes back the lancetmount 16 upward.

The cap 18 may be entirely formed of a transparent plastic material forexample. The cap 18 is formed, at the end thereof, with an opening 18 b.The cap 18 is fitted outwardly to the lower cover 10 b of the main case10. The cap 18 has an accommodation space 18 a for accommodating thepointed tip B1 of the lancet B projecting through the lower opening 10Bof the under cover 10. In sampling blood, the end of the cap 18 ispressed against the skin of the user to close the opening 18 b.

The cap 18 is provided with an O-ring 18 c for providing airtightness ofthe accommodation space 18 a. Therefore, by closing the opening 18 bwith the skin, air is trapped in the accommodation space 18 a throughthe case chamber 10 c. The cap 18 is fitted over the lower cover 10 bvia threads (not shown) formed at the inner circumferential surface ofthe cap 18. The distance H from the opening 18 b to the pointed tip B1of the lancet B can be adjusted by varying the extent of screwing thecap 18.

The first latch mechanism 20 includes a first engagement member 21having a stopper 21 a corresponding to the engagement portion 12 a ofthe first plunger rod 12, and a latch spring 22 for biasing the stopper21 a radially toward the first plunger rod 12. The first engagementmember 21 is held as pressed against the outer circumferential surfaceof the first plunger rod 12. The latch spring 22 is provided at apredetermined position on the inner circumferential surface of the maincase 10.

The second latch mechanism 26 includes a second engagement member 27having a stopper 27 a corresponding to the engagement portion 15 a ofthe second plunger rod 15, and a latch spring 28 for biasing the stopper27 a radially toward the second plunger rod 15. The second engagementmember 27 is held as pressed against the outer circumferential surfaceof the second plunger rod 15. The latch spring 28 is provided at apredetermined position on the inner circumferential surface of the maincase 10.

The release mechanism 30 releases the first and the second plunger rods12, 15 from the state restricted by the first and the second latchmechanisms 20, 26, respectively. The release mechanism 30 includes arelease button 31 engaging the first and the second engagement members21, 27 at positions opposite to the latch springs 22, 28, respectively,for simultaneously biasing these radially outward, a support member 32for supporting the release button 31 within the case chamber 10 c, and ashield member 33 interposed for keeping the airtightness between therelease button 31 and the case chamber 10 c. The release button 31includes a push portion 31 a projecting from a predetermined portion ofthe side surface of the main case 10. The shield member 33 comprises afilm formed of a rubber for example.

The vacuum relief mechanism 40 serves to release the vacuum condition inthe case chamber 10 c after pushing the release button 31. As shown inFIG. 3, the vacuum relief mechanism 40 comprises a vacuum relief button41 having a push portion 41 a projecting through a port 10 d provided atthe side surface of the main case 10, a vacuum relief spring 42 forelastically biasing a flange portion 41 b of the vacuum relief button 41in facing relationship to the port 10 d, and a nut 43 for holding thevacuum relief spring 42 within the case chamber 10 c.

Next, the use and operation of the body fluid sampler A will bedescribed with reference to FIGS. 2 and 4-8.

In the state shown in FIG. 2 (initial state), the stopper 21 a, 27 a ofthe first and the second engagement members 21, 27, are pressed againstthe first and the second plunger rods 12, 15, respectively, by theelastic biasing force of the relevant latch springs 22, 28.

In this state, the user performs a first operation. Specifically, theuser pushes the upper end 11 a of the piston 11 with the thumb forexample to push down the piston 11. At this time, the user need notbring the opening 18 b of the cap 18 into pressing contact with theskin. As a result, the piston 11 together with the first plunger rod 12moves downward against the elastic restoring force of the first spring13. Further, the second spring 14 and the second plunger rod 15 movedownward accompanying the first plunger rod 12. In this case, the volumein the case chamber 10 c gradually decreases as the bottom portion 11 bof the piston 11 moves downward.

As shown in FIG. 4, when the piston 11 is progressively moved downward,the engagement portion 15 a of the second plunger rod 15 comes intoengagement with the stopper 27 a of the second engagement member 27,making a click to be heard by the user. In this state, the secondplunger rod 15 is unable to further move downward. At this time, thelower end 15 b of the second plunger rod 15 is held in contact with thelancet mount 16 or held as slightly spaced therefrom.

As shown in FIG. 5, when the piston 11 is further depressed, theengagement portion 12 a of the first plunger rod 12 comes intoengagement with the stopper 21 a of the first engagement member 21,making a click to be heard by the user. In this state, the first plungerrod 12 is unable to further move upward. At this time, the second spring14 is compressed between the first plunger rod 12 and the second plungerrod 15, thereby storing a sufficient elastic restoring force.

In this way, when the piston 11 is pushed downward, the engagementportion 15 a of the second plunger rod 15 first engages the stopper 27a, and the engagement portion 12 a of the first plunger rod 12 thenengages the stopper 21 a. For realizing such stepwise engaging movement,in the initial state of the plunger rods 12, 15, the distance betweenthe vertically spaced two engagement portions 12 a, 15 a is set largerthan the distance between the stoppers 21 a and 27 a of the first andthe second engagement members 21, 27.

A preliminary operation before launching the lancet B is completed inthe above-described manner. In this state, since the engagement portions12 a, 15 a of the first and the second plunger rods 12, 15 are held inengagement with the stoppers 21 a, 27 a, respectively, the releasebutton 31 slightly projects outward. The first spring 13 is tensionedapproximately to its maximum length, and the volume in the case chamber10 c is kept minimum because the bottom portion 11 b of the piston 11has moved to the lowest limit position.

Subsequently, as shown in FIG. 6, the body fluid sampler A is pressedagainst the skin S to close the opening 18 b of the cap 18 with theskin. Then, as a second operation, the release button 31 is pushed bythe user radially of the main case 10. FIG. 6 illustrates the stateimmediately after the release button 31 is pushed.

As a result, the first and the second plunger rods 12, 15 which havebeen restricted by the first and the second engagement members 21, 27are simultaneously released from the respective stoppers 21 a, 27 a. Thefirst and the second plunger rods 12, 15 quickly move upward anddownward, respectively, in a mutually repelling manner due to theelastic restoring force of the second spring 14. Thus, the secondplunger rod 15 strongly hits or pushes the lancet mount 16 downward.Therefore, the pointed tip B1 of the lancet B integrally provided on thelancet mount 16 moves toward the opening 18 b to instantaneously stabthe skin S. Then, the pointed tip B1 of the lancet B is removed from theskin S due to the elastic restoring force of the third spring 17.

On the other hand, the first plunger rod 12 is pulled back and held at aposition close to the initial position together with the piston 11pulled back upward due to the elastic restoring force of the firstspring 13. At this time, the opening 18 b of the cap 18 of the casechamber 10 c is closed with the skin S. Therefore, as the piston 11moves upward, the volume of the case chamber 10 c gradually increases.

The pressure in the case chamber 10 c is reduced to a subatmosphericpressure so that the pressure in the accommodation space 18 a of the cap18, which communicates with the case chamber 10 c, is also reduced.Since the shield member 33 is provided at the clearance between therelease button 31 and the case chamber 10 c, the case chamber 10 c isprevented from air leakage relative to the outside. Therefore, the skinS closing the opening 18 b of the cap 18 bulges due to the suction ofthe vacuum. As a result, bleeding is accelerated from the portionstabbed by the pointed tip B1 of the lancet B. The bleeding state can beobserved by the user through the transparent cap 18.

Next, as a third operation, the vacuum relief button 41 of the vacuumrelief mechanism 40 is pushed by the user, as shown in FIGS. 7 and 8. Asa result, air is introduced from the outside through the port 10 dformed in the main case 10 and a hole 43 a of the nut 43 into the casechamber 10 c. Thus, the pressure in the case chamber 10 c returns to theinitial atmospheric pressure. Similarly, the pressure in theaccommodation space 18 a communicating with the case chamber 10 creturns to the atmospheric pressure. Therefore, the skin S closing theopening 18 b of the cap 18 is relieved from the vacuum sucked state.Therefore, the opening 18 b of the cap 18 can be easily removed from theskin S.

In this way, according to the body fluid sampler A, the preparation forlaunching the lancet B can be completed by one-push operation. Further,the subsequent launching of the lancet B can be completed just by oncepushing the release button 31. The first operation of pushing down thepiston 11 can be performed under the atmospheric pressure. Therefore,the user needs only to push down the piston 11 by a predetermined strokewithout using a strong force. Thus, the user can operate the apparatuseasily without anxiety.

The vacuum state of the case chamber 10 c is relieved by pushing thevacuum relief button 41. The vacuum relief button 41 is providedseparately from the release button 31 for launching the lancet B, whichdecreases the possibility of erroneously launching the lancet B.Therefore, the user can handle the apparatus safely.

It is to be noted that the present invention is not limited to theabove-described embodiment. For example, although coiled springs areutilized for launching the lancet B and for reducing the pressure in thecase chamber 10 c, any other elastic members may be used if only theycan be elastically compressed and restored sufficiently.

Moreover, although the body fluid sampler A is preferably used forself-sampling blood, the apparatus may be used for sampling body fluidother than blood, which can be sampled through the skin.

What is claimed is:
 1. A body fluid sampler comprising: a cylindricalmain case having a first end provided with a first opening and a secondend provided with a second opening; a piston inserted in the main caseto project from the first opening for movement within the main caseairtightly with respect to an inner wall of the main case; a firstplunger rod extending integrally from the piston toward said second end;a first elastic member for elastically urging the piston toward saidfirst end; a second plunger rod extending from the first plunger rodtoward said second end for movement within the main case with acompressible second elastic member interposed between the first plungerrod and the second plunger rod; a lancet mount associated with thesecond plunger rod adjacent to said second end for movement within themain case, the lancet mount being provided with a lancet oriented towardsaid second end; a third elastic member for elastically urging thelancet mount toward said first end; a latch mechanism which works, whenthe piston is pushed down for movement toward said second end togetherwith the first plunger rod, for restricting movement of the secondplunger rod toward said second end against a pushing force of the secondelastic member and for restricting rebounding of the piston and firstplunger rod which have been moved toward said second end while allowingthe second elastic member to be compressed; and a release mechanism forreleasing the first plunger rod and second plunger rod which have beenlatched by the latch mechanism.
 2. The body fluid sampler according toclaim 1, wherein the latch mechanism includes: a first and a secondengagement members each of which has a stopper for stopping acorresponding one of the first and the second plunger rods; a latchingelastic member for elastically biasing each of the engagement memberstoward the corresponding one of the first and the second plunger rods;and engagement portions respectively formed on the first and the secondplunger rods, the engagement portions being spaced from each other by adistance which is larger than a distance between the stoppers when theplunger rods are held in an initial state; the release mechanismincluding: a release button for simultaneously releasing the stoppersfrom the corresponding engagement portions against an elastic biasingforce of the latching elastic member.
 3. The body fluid sampleraccording to claim 2, wherein the release button is provided with a pushportion projecting from a predetermined portion of a side surface of themain case while keeping airtightness relative to the main case.
 4. Thebody fluid sampler according to claim 1, wherein the main case isprovided with a vacuum relief mechanism for relieving a vacuum statewithin the main case generated by pulling back the piston toward saidfirst end.
 5. The body fluid sampler according to claim 4, wherein thevacuum relief mechanism is provided with a vacuum relief buttonpartially projecting from a predetermined portion of a side surface ofthe main case, the vacuum relief button being elastically urged in theprojecting direction while keeping airtightness of the main case, thevacuum relief button being pushed against the elastic urging force forallowing air passage between inside and outside of the main case.
 6. Thebody fluid sampler according to claim 1, wherein the piston has an outercircumferential wall provided with an O-ring for closely contacting theinner wall of the main case.